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Search Results: 1 - 10 of 118544 matches for " Juha T. Peltoniemi "
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STERILE NEUTRINOS AS A SOLUTION TO ALL NEUTRINO ANOMALIES
Juha T. Peltoniemi
Physics , 1995,
Abstract: The sterile neutrino solutions to different irregular results and observations in neutrino physics are studied. It is pointed out that introducing sterile neutrinos helps to solve simultaneously the observed anomalies. It is argued that sterile neutrinos can solve the conflict between dark matter neutrinos, LSND result and supernova nucleosynthesis. Other supernova constraints for sterile neutrinos are revised. Possibilities to avoid the big bang nucleosynthesis constraints for sterile neutrinos are explored. It is claimed that sterile neutrinos can solve the crisis in big bang nucleosynthesis. It is pointed out that sterile neutrinos can provide a consistent explanation to the anomalies observed at Karmen. It is argued that sterile neutrinos are valid dark matter candidates. It is claimed that the conversions to sterile states are consistent solutions to both the solar and the atmospheric neutrino problems, and cannot be ruled out by cosmological or astrophysical arguments. Models for the masses and the interactions of sterile neutrinos are reviewed.
Sterile neutrinos and supernova nucleosynthesis
Juha T. Peltoniemi
Physics , 1995,
Abstract: The role of the sterile neutrinos to the r-process nucleosynthesis in supernova explosions is studied. Previously it has been argued that a large part of neutrino mixing can be excluded if the supernovae are the origin of the heavy elements. It is shown that a conversion to sterile neutrinos may evade those limits. The possibility that such conversions can enhance the nucleosynthesis is investigated. The desired mass spectrum is consistent with neutrino masses suggested by other observed phenomena, like the solar neutrino problem, the atmospheric neurino problem, dark matter and the LSND signals.
Radiative corrections to neutrino-majoron couplings
Juha T. Peltoniemi
Physics , 1995,
Abstract: It is claimed that radiative corrections maintain the proportionality between the neutrino mass and the neutrino-majoron coupling and never give rise to enhanced decay rates in conventional majoron models. The coupling of a majoron to neutrinos is calculated at one loop level in various models, including the singlet majoron model and the Zee model with a majoron. When the respective corrections to the mass matrix are taken into account the would-be non-diagonal terms in the neutrino-majoron coupling are rotated away. It is pointed out that the coincidence between neutrino mass matrices and neutrino-majoron couplings is not accidental, but is a general consequence of Noether's theorem. Noether's theorem also implies that the majoron coupling to charged fermions is always diagonal in the fermion mass basis, and it vanishes completely in the singlet majoron models.
Simulations of neutrino oscillations for a wide band beam from CERN to LENA
Juha Peltoniemi
Physics , 2009,
Abstract: Neutrino oscillations from a wide band beam of 1-6 GeV at CERN to LENA, a 50 kton liquid scintillator, at Pyhasalmi mine 2288 km apart are simulated. The performance is very promising and this can be considered as a realistic alternative for the next long baseline experiment. Different performance factors and baselines are compared and the studied setup is found to be sufficiently close to a realistic optimum.
Simulations of neutrino oscillations with a high-energy beta beam from CERN to LENA at Pyhasalmi Mine
Juha Peltoniemi
Physics , 2009,
Abstract: I consider a high-Q beta beam peaking at multi-GeV energy for the baseline CERN-Pyh\"asalmi, with the length of 2288 km, using LENA, a 50 kton liquid scintillator as the far detector. The beta beam is assumed to be accompanied by a conventional wide band beam of 1--6 GeV. This combination turns out to be very powerful to measure neutrino parameters if $\sin^2 2\theta_{13}\sim (1...3)\cdot 10^{-3}$.
Simulations of neutrino oscillations for a low-energy neutrino factory with a magnetized large-volume liquid scintillator at 2288 km baseline
Juha Peltoniemi
Physics , 2009,
Abstract: A magnetized large-volume liquid scintillator might be used as a tracking detector with charge identification to measure high-energy neutrinos. I consider neutrino oscillations for a beam from a low-energy neutrino factory to such a detector for the baseline CERN-Pyhasalmi, with the length of 2288 km. The range to study the oscillation parameters extends to $\sin^2 2\theta_{13}\sim 10^{-4}$ for reasonable assumptions for the detector and the beam.
Liquid scintillator as tracking detector for high-energy events
Juha Peltoniemi
Physics , 2009,
Abstract: A large-volume liquid scintillator can be used as a tracking detector to measure high-energy neutrino events, like atmospheric neutrinos and neutrino beams. The lepton flavor recognition is almost absolute above 1 GeV. The energy resolution is 2--5 %, the main uncertainties coming from nuclear physics and poorly recognized hadrons. At GeV scale antineutrinos may be statistically distinguishable from neutrinos by neutron and proton signals.
Acquisition of Bidirectional Reflectance Factor Dataset Using a Micro Unmanned Aerial Vehicle and a Consumer Camera
Teemu Hakala,Juha Suomalainen,Jouni I. Peltoniemi
Remote Sensing , 2010, DOI: 10.3390/rs2030819
Abstract: This paper describes a method for retrieving the bidirectional reflectance factor (BRF) of land-surface areas, using a small consumer camera on board an unmanned aerial vehicle (UAV) and introducing an advanced calibration routine. Images with varying view directions were taken of snow cover using the UAV. The vignetting effect was corrected from the images, and reflectance factor images were calculated using a calibrated white target as a reference. After spatial registration of the images using a corresponding point method, the target surface was divided into a grid, and a BRF was generated for each grid element. Lastly a model was fitted to the BRF dataset for data interpretation. The retrieved BRF were compared to parallel ground measurements. Comparison showed similar BRF and reflectance factor characteristics, which suggests that accurate measurements can be taken with cheap consumer cameras, if enough attention is paid to calibration of the images.
Polarised Multiangular Reflectance Measurements Using the Finnish Geodetic Institute Field Goniospectrometer
Juha Suomalainen,Teemu Hakala,Jouni Peltoniemi,Eetu Puttonen
Sensors , 2009, DOI: 10.3390/s90503891
Abstract: The design, operation, and properties of the Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO) are presented. FIGIFIGO is a portable instrument for the measurement of surface Bidirectional Reflectance Factor (BRF) for samples with diameters of 10 – 50 cm. A set of polarising optics enable the measurement of linearly polarised BRF over the full solar spectrum (350 – 2,500 nm). FIGIFIGO is designed mainly for field operation using sunlight, but operation in a laboratory environment is also possible. The acquired BRF have an accuracy of 1 – 5% depending on wavelength, sample properties, and measurement conditions. The angles are registered at accuracies better than 2°. During 2004 – 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe. The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.
Neutrino propagation in matter using the wave packet approach
J. T. Peltoniemi,V. Sipilainen
Physics , 2000, DOI: 10.1088/1126-6708/2000/06/011
Abstract: We study the oscillations and conversions of relativistic neutrinos propagating in matter of variable density using the wave packet formalism. We show how the oscillation and coherence lengths are modified in comparison with the case of oscillations in vacuum. Secondly, we demonstrate how the equation of motion for two neutrino flavors can be formally solved for almost arbitrary density profile. We calculate finally how the use of wave packets alters the nonadiabatic level crossing probabilities. For the most common physical environments the corrections due to the width of the wave packet do not lead to observable effects.
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